Thanks Jeff, I will check the ohms. Temp sensor did occur to me but the
intermittent bit made me rethink it. There are two 'sensor' things sticking
into the oven. One is unprotected and the other is supported by a single
brace. I suspect the supported one is the smoke preventer (forget what the
schematic calls it). The sensor has two white wires to it, so I think I have
the right one. But when I disconnected the sensor, and powered up there was
an error code which hadn't been there before. I'll let you know whatever
happens.
BM